Redis menyediakan high availability melalui replication (replica meniru data), Redis Sentinel (monitoring automatic failover), dan Redis Cluster (sharding + replication). Memahami ini penting untuk menjalankan Redis secara andal dalam production.
Replication — primary dan replicas
PRIMARY (master) → handles writes; asynchronously replicates data to replicas
REPLICAS (slaves) → copies of the primary's data; can serve READS (read scaling)
Write → Primary → async replication → Replicas (eventually consistent)
✓ Redundancy (replicas have copies) + read scaling (reads offloaded to replicas)
✗ Replication is ASYNC → a small lag; a failover could lose very recent writes
